CN110272718A - Al@MnO2Composite material, preparation method and application thereof - Google Patents

Abstract

The invention discloses an Al@MnO ₂ composite material, a preparation method and an application thereof; the Al@MnO ₂ composite material is synthesized by a simple one-step chemical method, and MnO ₂ nanoparticles are uniformly distributed on the surface of an Al sheet. The method adopts a simple one-step hydrothermal method, does not add surfactants, and does not use complex instruments to avoid traditional methods such as metal steam and ball milling, has less pollution, and is easy to control, and can be widely used in industrial production. A vector network analyzer was used to test the microwave absorption parameters of the composite material, and the microwave reflection loss of the composite material was calculated by the classical coaxial line theory. The infrared stealth performance was tested by a dual-band emissivity measuring instrument. The results show that the Al@MnO ₂ composite microwave absorbing material has excellent microwave absorbing properties and infrared stealth properties.

Description

Al@MnO2 composite material, preparation method and application

technical field

The invention relates to the technical field of composite materials, in particular to an Al@MnO ₂ composite material, a preparation method and applications thereof.

Background technique

Both microwave and infrared radiation belong to electromagnetic waves, but they belong to different wavebands, so microwave and infrared radiation have different physical properties. The working principle of the radar detector is that the reflected waves generated on the surface of the target object are received by the radar. The working principle of the infrared detector is: the energy radiated by the target object itself is accepted by the detector. Because the detection principles of the two are diametrically opposite, the mechanisms of microwave and infrared radiation are also different. Microwave stealth requires materials with high absorption and low reflection, while low infrared radiation requires materials with high reflection and low emission. Therefore, there are relatively few materials for microwave infrared compatible stealth materials.

But fortunately, the frequency bands of the two are different. Generally, the microwave frequency is 2-18 GHz, while the infrared band is 8-14 μm, which makes it possible to study microwave-infrared compatible stealth materials.

Flake Al powder is widely used in low infrared radiation materials due to its low infrared emissivity. The semiconductor oxide MnO ₂ has excellent catalytic and electrochemical properties, ion exchange and other properties. Therefore, it is a very good dielectric material with good wave-absorbing properties.

SUMMARY OF THE INVENTION

Based on the technical problems existing in the background technology, the present invention proposes an Al@MnO ₂ composite material, a preparation method and an application thereof. The Al@MnO ₂ composite material is prepared by a simple one-step chemical reaction, and the material is compatible with microwave absorption and low infrared radiation properties. .

The MnO ₂ nanoparticles in the Al@MnO ₂ composite material proposed by the present invention are uniformly distributed on the surface of the Al powder.

The method steps for preparing the Al@ _MnO composite material proposed by the present invention are as follows:

S1: Pretreatment of Al powder: add Al powder to the container, and then add acetone to react. After the reaction is finished, suction filtration, washing, and vacuum drying to obtain Al powder with pure surface;

S2: Synthesis of Al@MnO ₂ composite material: Add the Al powder treated in S1 and distilled water into the container, slowly add KMnO ₄ into the container under magnetic stirring, and filter immediately when the purple color of the solution completely fades , washed 3-5 times with distilled water and absolute ethanol, and vacuum-dried the washed product to obtain the Al@MnO ₂ composite material.

Preferably, the mass volume ratio of Al powder and acetone in the S1 is 2-5g:150ml.

Preferably, the reaction conditions in the S1 are: the temperature is 20-25°C, and the time is 20-28h.

Preferably, the conditions of vacuum drying in the S1 are: vacuum degree 0.06-0.085MPa, temperature 50-70°C, time 20-28h.

Preferably, the mass-volume ratio of aluminum powder, potassium permanganate and deionized water in the S2 is (0.3-0.7) g:(0.1-0.5) g:60ml.

Preferably, the conditions of magnetic stirring in the S2 are as follows: the rotational speed is 500-1000 r/min, the temperature is 20-25° C., and the time is 3-7 min.

Preferably, the conditions of vacuum drying in the S2 are: vacuum degree 0.06-0.085Mpa, temperature 50-70°C, time 20-28h.

The application of the Al@MnO ₂ composite material proposed in the present invention in the wave absorbing material.

Mechanism of action:

The Al@MnO ₂ composite material has a core-shell structure, and the MnO ₂ nanoparticles are closely dispersed on the Al sheet, so that the Al sheet is layered to form a three-dimensional structure containing many cavities, which not only improves the impedance matching of the Al powder, but also enables the electromagnetic wave to be smoothly Entering the material is also conducive to the multiple reflection and scattering of electromagnetic waves inside the material. This three-dimensional cavity structure can also induce resonance effects, space charge polarization, electron relaxation polarization and other effects, thereby increasing the microwave absorption performance of the material. The infrared emissivity of flake Al powder is lower, and Al is still flake, which also provides a guarantee for the lower infrared emissivity of the material. In view of the high crystallinity of MnO ₂ nanoparticles, the formation of nano-scale MnO ₂ particles can enhance the electronic polarization and interface polarization of the composite, and have a certain promotion effect on the dielectric loss of the composite. The existence of _MnO2 nanoparticles in the composite greatly improves the impedance matching of the material, which not only increases the surface roughness of the Al sheet, promotes the scattering during microwave propagation, but also enlarges the cavity between the Al sheets , which makes the resonance effect possible. To some extent, a heterointerface is also formed between the semiconducting _MnO2 and the conductive metal Al sheet, which provides the possibility for interfacial polarization during electron migration.

Compared with the prior art, the beneficial effects of the present invention are reflected in:

1. In the present invention, the Al@MnO ₂ composite material is synthesized by a simple chemical method, and the MnO ₂ nanoparticles are uniformly distributed on the surface of the Al sheet.

2. The present invention does not add surfactant, and also avoids traditional methods such as metal steam and ball milling, with little pollution, easy reaction control, and can be widely used in industrial production.

3. The preparation method is simple, and the present invention adopts a simple one-step hydrothermal method to successfully combine Al and MnO ₂ . And the prepared nanocomposite does not need other subsequent treatment, such as calcination under protective gas atmosphere.

4. The lightweight nanocomposites prepared by mixing with paraffin have excellent absorbing properties and can be used in the field of high temperature absorbing. They have the characteristics of light weight and strong bearing capacity. It has high theoretical and practical value and has a good application prospect due to the requirements of light weight, strong wave absorbing ability and wide absorption frequency band.

Description of drawings

Fig. 1 is the XRD pattern of Al@ _MnO nanocomposite material of the present invention;

Fig. 2 is the SEM image of Al@ _MnO nanocomposite material of the present invention;

Fig. 3 is the TEM image of the Al@ _MnO nanocomposite material of the present invention;

FIG. 4 is a graph showing the variation of the reflection loss value with frequency of the Al@MnO ₂ nanocomposite material S1 of the present invention;

FIG. 5 is a graph showing the change of the reflection loss value of the Al@MnO ₂ nanocomposite material S2 with frequency of the present invention;

6 is a graph showing the change of the reflection loss value of the Al@MnO ₂ nanocomposite material S3 with frequency of the present invention;

FIG. 7 is a graph showing the variation of the reflection loss value with frequency of the Al@MnO ₂ nanocomposite material S4 of the present invention;

FIG. 8 is a graph showing the variation of the reflection loss value with frequency of the Al@MnO ₂ nanocomposite material S5 of the present invention;

FIG. 9 is a graph showing the variation of the reflection loss value with frequency of the Al@MnO ₂ samples S1-S5 of the present invention when the thickness is 1 mm;

FIG. 10 is a comparison chart of the infrared emissivity of the Al@MnO ₂ samples S1-S5 of the present invention.

Detailed ways

The present invention will be further explained below in conjunction with specific embodiments.

Source of raw materials

Flake Al powder, industrial grade, purchased from Shanghai Zhongyou Quanfa Powder Material Co., Ltd.;

Potassium permanganate, analytical grade, purchased from Sinopharm Chemical Reagent Co., Ltd.;

Acetone, analytically pure, was purchased from Jiangsu Qiangsheng Functional Chemical Co., Ltd.;

Anhydrous ethanol, analytical grade, was purchased from Sinopharm Chemical Reagent Co., Ltd.

Example 1

The method steps for preparing the Al@ _MnO composite material proposed by the present invention are as follows:

S1: Pretreatment of Al powder: add 2 g of flake Al powder to a three-necked flask, then add 150 ml of acetone, and react at 20° C. for 20 h. After the reaction is completed, suction filtration, washing, and vacuum drying to obtain Al powder with pure surface. The vacuum drying conditions are: vacuum degree 0.06MPa, temperature 50°C, time 20h;

S2: Synthesis of Al@MnO ₂ composite material: Weigh 0.3 g of the Al powder treated in S1, add 60 ml of distilled water into the container, and slowly add 0.1 g KMnO ₄ into the container under magnetic stirring, when the solution turns purple Immediately suction filtration when the color fades completely, wash 4 times with distilled water and absolute ethanol, and vacuum dry the washed product to obtain Al@MnO ₂ composite material. The vacuum drying conditions are: vacuum degree 0.06Mpa, temperature 50°C, time 20h, the conditions of magnetic stirring are: rotating speed 500r/min, temperature 20℃, time 3min.

Example 2

The method steps for preparing the Al@ _MnO composite material proposed by the present invention are as follows:

S1: Pretreatment of Al powder: add 5 g of flake Al powder to a three-necked flask, then add 150 ml of acetone, and react at 20° C. for 24 h. After the reaction is completed, suction filtration, washing, and vacuum drying to obtain Al powder with pure surface. The vacuum drying conditions are: vacuum degree 0.07MPa, temperature 60°C, time 24h;

S2: Synthesis of Al@MnO ₂ composite material: Weigh 0.5 g of the Al powder treated in S1, add 60 ml of distilled water into the container, and slowly add 0.2 g KMnO ₄ into the container under magnetic stirring, when the solution turns purple Immediately after fading, suction filtration, washed with distilled water and absolute ethanol for 4 times, and vacuum-dried the washed product to obtain Al@MnO ₂ composite material. The vacuum drying conditions are: vacuum degree 0.07Mpa, temperature 60°C, time 24h, the conditions of magnetic stirring are: rotation speed 700r/min, temperature 20℃, time 5min.

Example 3

The method steps for preparing the Al@ _MnO composite material proposed by the present invention are as follows:

S1: Pretreatment of Al powder: add 5 g of flake Al powder to a three-necked flask, then add 150 ml of acetone, and react at 22° C. for 24 h. After the reaction is completed, suction filtration, washing, and vacuum drying to obtain Al powder with pure surface. The vacuum drying conditions are: vacuum degree 0.07MPa, temperature 60°C, time 24h;

S2: Synthesis of Al@MnO ₂ composite material: Weigh 0.5 g of the Al powder treated in S1, add 60 ml of distilled water into the container, and slowly add 0.3 g KMnO ₄ into the container under magnetic stirring, when the solution turns purple Immediately after fading, suction filtration, washed with distilled water and absolute ethanol for 4 times, and vacuum-dried the washed product to obtain Al@MnO ₂ composite material. The vacuum drying conditions are: vacuum degree 0.07MPa, temperature 60℃, time 24h, the conditions of magnetic stirring are: rotation speed 700r/min, temperature 25℃, time 5min.

Example 4

The method steps for preparing the Al@ _MnO composite material proposed by the present invention are as follows:

S1: Pretreatment of Al powder: add 3 g of flake Al powder to a three-necked flask, then add 150 ml of acetone, and react at 20° C. for 24 h. After the reaction is completed, suction filtration, washing, and vacuum drying to obtain Al powder with pure surface. The vacuum drying conditions are: vacuum degree 0.06MPa, temperature 60°C, time 24h;

S2: Synthesis of Al@MnO ₂ composite material: Weigh 0.5 g of the Al powder treated in S1, add 60 ml of distilled water into the container, and slowly add 0.4 g KMnO ₄ into the container under magnetic stirring, when the solution turns purple Immediately after fading, suction filtration, washed with distilled water and absolute ethanol for 4 times, and vacuum-dried the washed product to obtain Al@MnO ₂ composite material. The vacuum drying conditions are: vacuum degree 0.07Mpa, temperature 60°C, time 26h, the conditions of magnetic stirring are: rotation speed 700r/min, temperature 25°C, time 5min.

Example 5

The method steps for preparing the Al@ _MnO composite material proposed by the present invention are as follows:

S1: Pretreatment of Al powder: add 5g of flake Al powder to a three-necked flask, then add 150ml of acetone, and react at 25°C for 28h. After the reaction is completed, suction filtration, washing, and vacuum drying to obtain Al powder with pure surface. The vacuum drying conditions are: vacuum degree 0.085MPa, temperature 70°C, time 28h;

S2: Synthesis of Al@MnO ₂ composite material: Weigh 0.7 g of the Al powder treated in S1, add 60 ml of distilled water into the container, and slowly add 0.5 g KMnO ₄ into the container under magnetic stirring, when the solution turns purple Immediately suction filtration when the color fades completely, wash 4 times with distilled water and absolute ethanol, and vacuum dry the washed product to obtain Al@MnO ₂ composite material. The vacuum drying conditions are: vacuum degree 0.085Mpa, temperature 70°C, time 28h, the conditions of magnetic stirring are: rotation speed 1000r/min, temperature 25℃, time 7min.

Performance Testing

XRD test: The crystal structure of the sample was characterized by a LabX XRD-6000 X-ray diffractometer, in which the X-ray was Cu-Kα ray, wavelength 0.154nm, step size 0.02°, light tube current 36kV, current 30mA, scanning angle 20-80°, scanning speed 2°/min ^-1 .

Scanning electron microscope test: take a small amount of the prepared sample into deionized water, ultrasonically disperse it, drop it on the conductive adhesive, stick it on the sample table and dry it, and use the FEI-Sirion200 field emission scanning electron microscope to characterize the morphology of the sample.

Transmission electron microscope test: JEOL-2010 transmission electron microscope was used to characterize the microstructure of the samples. Take a small amount of sample to ultrasonically disperse in deionized water, drop onto the copper mesh, dry, inject and test.

Microwave absorption performance test: Using a vector network analyzer, VNA, AV3629D, China, to measure the electromagnetic parameters of the sample, the test frequency range is 2-18GHz. The sample and paraffin were mixed in a mass ratio of 3:1, heated and melted at 80 °C, and then poured into a copper ring mold to make a coaxial ring with a thickness of 2.0mm, an outer diameter of 7mm and an inner diameter of 3.04mm. test.

Dual-band emissivity measuring instrument: IR-2, measured infrared absorption performance by Shanghai Institute of Technical Physics, Chinese Academy of Sciences.

Result analysis

Figure 1 is a XRD comparison chart. S1-S5 in Fig. 1 correspond to the Al@MnO ₂ composites of Examples S1-S5, respectively. It can be seen from Figure 1 that all samples (S1-S5) have strong characteristic peaks corresponding to Al (JCPDS No.04-0787), and the four strong characteristic peaks are located at 2θ=38.47°, 44.74°, 65.13°, respectively. and 78.23°, corresponding to the crystal planes: (111), (200), (220) and (311). However, the characteristic peaks of MnO ₂ were not found, which may be due to the small particle size of the MnO ₂ nanoparticles, the dispersion and the thin attachment thickness, resulting in no peaks in XRD; it may also be because the characteristic peaks of MnO ₂ are relative to the characteristic peaks of Al The intensity is too weak, causing the characteristic peaks to be masked by aluminum and not detected. The results show that there are no other impurity peaks in the ₅ samples (S1-S5), and the intensity of the characteristic peaks of Al gradually weakens with the increase of the amount of KMnO4 added.

Figure 2 is the SEM image of the Al@MnO ₂ composite material, which corresponds to Figure 3. It can be seen from Figure 3 that the MnO ₂ nanoparticles are uniformly distributed on the surface of the Al sheet. The size of the Al sheet is tens of microns and the thickness is less than 1 μm. The granular MnO ₂ is attached to the surface of the Al sheet, so that the Al sheet is layered to form a three-dimensional structure containing many cavities. The cavity structure not only improves the impedance matching of the Al powder, so that the electromagnetic wave can enter the material smoothly, but also facilitates the multiple reflection and scattering of the electromagnetic wave inside the material. This three-dimensional cavity structure can also induce a resonance effect, thereby increasing the microwave of the material. Absorption properties. The infrared emissivity of the flake Al powder is low. It can be seen from the figure that the Al is still flake, which also provides a guarantee for the low infrared emissivity of the material.

Figure 3 is the TEM image of Al@ _MnO2 . The morphological features of the Al@ _MnO composites can be observed by transmission microscopy with high resolution, as shown in Figure 4. It can be seen from Fig. 4 that the Al@MnO ₂ composite has a core-shell structure with a size of about 50 nm, and MnO ₂ nanoparticles with a particle size of 3-4 nm are closely dispersed on the Al sheet. Zooming in on the box in Fig. 4(a) results in a high-resolution lens in Fig. 4(b), in which highly crystalline _MnO2 nanoparticles can be seen, and the lattice spacing 0.25 nm in the figure is very high. The good one corresponds to the (111) crystal plane in the fluorite-structured _MnO2 , which again proves the successful synthesis of _MnO2 . The formation of nano-scale _MnO particles content can enhance the electronic polarization and interface polarization of the composite, which further promotes the dielectric loss of the composite.

Figures 4-9 are microwave absorption comparison diagrams. As shown in the figure, the maximum return loss values of S1-S5 are -23.57dB, -42.93dB, -30.99dB and -26.90dB, respectively, but the effective absorption bandwidth below -10dB is not very ideal. Figure 9 shows the RL curves of samples S1-S5 when the thickness is 1 mm. The maximum RL value of the sample increases first and then decreases with the increase of the mass fraction of MnO _2. The S2 sample reaches the maximum -42.93 dB at 12.72 GHz, and its The effective absorption bandwidth is only 1.28GHz (12.08-13.36GHz). Since the impedance matching of a single Al powder is not good, the impedance matching of the Al@MnO ₂ composite can be effectively adjusted by adjusting the mass fraction of MnO ₂ , so that the electromagnetic wave can be more easily incident on the material. It can be seen from the microwave absorbing properties of the samples that the microwave absorption intensity of the Al@MnO ₂ composite material reaches below -10dB at low thickness, but the effective absorption bandwidth is relatively narrow, which may be because the material is mainly resonant absorption, which cannot be Take full advantage of the properties of the material. In addition, the Al@ _MnO2 composite not only has good microwave absorption properties, but also has low infrared radiation properties due to the existence of flake Al powder.

Figure 10 is a comparison chart of infrared emissivity. The infrared emissivity of S1-S5 is 0.55, 0.59, 0.61, 0.65 and 0.72, respectively, the content of Al decreases relatively with the increase of the mass fraction of _MnO2 , and the infrared emissivity gradually increases. As we all know, the lower the infrared emissivity, the lower the infrared radiation. Therefore, the S2 sample is a composite material with good microwave absorption and low infrared radiation compatibility, with the best microwave absorption and lower infrared radiation performance.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. The equivalent replacement or change of the inventive concept thereof shall be included within the protection scope of the present invention.

Claims (9)

1.Al@MnO₂Composite material, which is characterized in that the MnO in the composite material₂Nano particle is evenly distributed on Al powder Surface.

2. a kind of Al@MnO described in claim 1₂The preparation method of composite material, which is characterized in that method and step is as follows:

The pretreatment of S1:Al powder: being added Al powder in a reservoir, adds acetone reaction.To after reaction, filter, washing, very Sky is dry, obtains the pure Al powder in surface；

S2:Al@MnO₂The synthesis of composite material: treated in S1 Al powder, distilled water are added in container, in magnetic force By KMnO under stirring₄It is slowly added in container, is filtered immediately when the purple of solution fades completely, with distilled water and dehydrated alcohol Washing 3-5 times, it is dry to the product vacuum after washing to get Al@MnO₂Composite material.

3. Al@MnO according to claim 2₂The preparation method of composite material, which is characterized in that Al powder and third in the S1 The mass volume ratio of ketone is 2-5g:150ml.

4. Al@MnO according to claim 2₂The preparation method of composite material, which is characterized in that the reaction item in the S1 Part are as follows: 20-25 DEG C of temperature, time 20-28h.

5. Al@MnO according to claim 2₂The preparation method of composite material, which is characterized in that be dried in vacuo in the S1 Condition are as follows: vacuum degree 0.06-0.085MPa, 50-70 DEG C of temperature, time 20-28h.

6. Al@MnO according to claim 2₂The preparation method of composite material, which is characterized in that aluminium powder, height in the S2 Potassium manganate and the mass volume ratio of deionized water are (0.3-0.7) g:(0.1-0.5) g:60ml.

7. Al@MnO according to claim 2₂The preparation method of composite material, which is characterized in that magnetic agitation in the S2 Condition are as follows: revolving speed 500-1000r/min, 20-25 DEG C of temperature, time 3-7min.

8. Al@MnO according to claim 2₂The preparation method of composite material, which is characterized in that be dried in vacuo in the S2 Condition are as follows: vacuum degree 0.06-0.085Mpa, 50-70 DEG C of temperature, time 20-28h.

9. a kind of Al@MnO as described in claim 1₂Application of the composite material in absorbing material.